Institute of Experimental and Clinical Pharmacology and Toxicology, Ruprecht-Karls-University of Heidelberg, Mannheim, Germany

Abstract: This is the first report in which seasonal patterns in nativity and mortality were analyzed in a single family, branches of which have resided in the middle of Europe as well as in South Africa for several hundreds of years. The family included a total of 3,645 members. The data convincingly demonstrate the effect of the seasonal amplitude of the photoperiod, as represented by the different latitudes, on the seasonal rhythm in nativity and mortality, discernible from 1500–1950 in Europe at 51° N but not in South Africa at 30° S. Most interestingly, this pattern in Germany was lost in the second half of the 20th century, possibly because of socioeconomic conditions and masking effects from the introduction of new technology to better control environmental conditions, greater use of artificial light, further incorporation of shiftwork schedules in industry, stronger advances in medical treatment of many diseases (including increased availability of intensive care in hospitals), and finally, greater longevity of the population.